U.S. Pat. 4,773,372 discloses an internal combustion engine having at least two power-adjusting elements which can be electrically driven independently of each other. In engines of this kind, different torque amounts of the cylinder banks can occur whose air is supplied via different power adjusting elements, that is, these cylinder banks have separate intake manifolds. The different torque amounts are caused by the different charges of the cylinders because the supplied air mass flow is dependent, inter alia, on the following: the geometry of the power-adjusting element (the throttle flap), the different characteristic lines of the actual value transducer of the power-adjusting element in so-called electronic gas pedal systems and/or on different leakage flows. The actual value transducer of the power-adjusting element can be a potentiometer of the throttle flap and the different leakage flows occur, for example, via the throttle flaps, the tank-venting valves, the crankcase venting, the exhaust-gas return valves, the brake amplifier, et cetera. The different cylinder charges which result therefrom and therefore the different torque amounts lead, however, to an operating performance of the engine which is not completely satisfactory.
It is an object of the invention to provide measures with the aid of which an equalization of the cylinder banks takes place with reference to the torque contributions thereof.
The method of the invention is for equalizing at least two cylinder banks of an internal combustion engine. The method includes the steps of: controlling each of the cylinder banks with at least one control variable; determining a quantity representing the torque contributions of the cylinder banks; and, correcting the at least one control variable in dependence upon the quantity in the sense of an equalization of the torque contributions of the cylinder banks.
U.S. Pat. 4,688,535 discloses the determination of a quantity, which represents the differences in the torque contributions of individual cylinders, by evaluating segment times and to supply this quantity for the equalization of the cylinders.
A procedure is provided with which the equalization of cylinder banks takes place in a simple manner with the air supply of the cylinders being influenced by power-adjusting elements controlled independently of each other. It is of special advantage that the cylinder equalization takes place via a corresponding equalizing intervention via the throttle flaps of the engine and that the ignition angle need not be shifted or shifted only to a limited extent for equalization. In this way, significantly greater torque differences between the cylinder banks can be compensated. In addition, fuel is saved because the ignition angle can be held in the optimal region and exhaust-gas emissions are reduced because the ignition angle can be used more for combustion optimization than for the cylinder equalization.
It is especially advantageous that especially in idle, the torque-increasing capability of an ignition angle shift remains ensured because the ignition angle is not applied or is only applied to a limited extent for cylinder equalization.